The present application relates to a separator and a battery including the separator, and more particularly, to a lamination-type separator.
Owing to the noticeable recent development of mobile electronic technology, electronic apparatuses such as cellular phones and notebook computers are recognized as basic technologies that support an advanced information society. Research and development in implementing a high level of functionality of such electronic apparatuses has been vigorously advanced, and the power consumption of these electronic apparatuses has increased in proportion thereto. On the other hand, long-term driving force is necessary for these electronic apparatuses. Accordingly, implementation of a high energy density of a secondary battery that is a driving power source thereof is necessarily desired. In addition, from the viewpoint of the volume occupied, the mass, and the like of a battery built into these electronic apparatuses, it is desirable that the energy density of the battery is as high as it possibly can be. Accordingly, currently, lithium-ion secondary batteries with a superior energy density are built into most apparatuses.
In the lithium-ion secondary battery, by opposing a positive electrode and a negative electrode through a separator, both safety and battery capability are implemented. However, considering the implementation of high capacity and high safety, in the related art it is difficult to obtain sufficient capability only by using a polyolefin microporous membrane. In other words, in a battery in which high capacity is implemented in accordance with an increase in the functionality of the electronic apparatus, the thickness of an electrode layer is increased. Accordingly, the expansion of the negative electrode increases at the time of the charging process. At this time, pressure is applied to the inside of a cell, the pores of the separator are crushed so as to decrease ion permeability. Therefore, in a case where compression resistance is low, it is difficult to obtain adequate battery characteristics.
Meanwhile, for example as in JP-A-2008-4536, there is disclosed the technology of employing a separator that has a dynamic hardness DH of 1000 or higher at a time when the indenter load reaches 12 kgf/cm2 in the composite membrane that is acquired by forming a coating layer formed from a polymer porous body having heat resistance on at least one face of a polyolefin microporous membrane.